This invention relates to a handled plastic container in which the container is formed by blow moulding a preform and the handle is separately formed and then connected to the container during the container forming process.
Plastic containers for holding liquids including beverages and other domestic liquids are in wide spread use. During the 1980""s plastic largely replaced glass as the material of first preference for the packaging of carbonated soft drinks. Plastics such as polyethylene terephthalate (PET) offer significant savings when compared with glass in packaging such products. Plastic is lighter than glass and plastic bottles are cheaper to make and cheaper to transport than glass bottles. In addition, there are clear safety advantages when using plastic given the inherent problems with breakages when using glass. Plastic containers are also in wide use for products such as detergents and fruit juices. Such products are generally packaged in one or two litre containers with relatively large outlet openings. For ease of pouring, containers such as those made from PVC often include a handle. In the past, the handle in plastic containers formed by extrusion blow moulding have been provided by blow moulding a hollow and integral handle portion into the container side wall. Given the constraints of container design, such handles are generally quite broad and often leave little room for one to firmly grasp the inside of the handle. Special moulds are required in the production of such bottles, they are more difficult to blow mould than a non handled bottle and there are difficulties with stress concentrations leading to possible container failure in the areas near the junction of the handle with the rest of the container.
In addition, it has not been generally possible to economically produce such handled bottles from synthetic polyesters such as PET. To extrusion blow mould PET it would be necessary to use a resin having a high intrinsic viscosity (i.e. well over 1.0). Such containers would not have the same degree of side wall orientation as a container stretch blow moulded from a preform. If an integral handle was formed in a PET container formed from a preform, special cutting tooling would be required to remove the flashing formed between the container side wall and the integrally formed handle due to the high orientation of the material.
An alternative is the use of a separate handle joined to the container. If a separate handle is utilised it is possible to injection mould a handle which is narrower and thinner than the integral handles of the previously described blow moulded containers and if adequately attached to the container such handle designs are more effective and easier to use.
Various attempts have been made to attach separate handles to blow moulded containers formed from preforms but these have not been altogether successful. One difficulty has been inadequate engagement of the handle with the blow moulded container. A further difficulty has been the relative slowness of the processes used to produce such containers.
It is an object of the present invention to provide a method of securing a separate handle to a plastic blow moulded container which enables relatively rapid manufacture and which leads to the production of a handled bottle where the handle is firmly secured.
In accordance with the present invention, the applicants have developed a modified preform having a moulded engagement portion adapted to engage with part of a separately formed handle. In the past, it has been proposed that such handles be connected to the plastic container by blow moulding the walls of the container around retaining portions provided at the respective ends of the handle. For example, reference is made to Australian patent 637,696. The present invention provides for engagement of at least part of the handle with an engagement portion which is preferably rigid and which is not subject to stretching during the blow moulding process.
Thus, in accordance with one aspect of the present invention there is provided a method of manufacturing a handled plastic container which includes the steps of:
(a) positioning a preformed handle and a synthetic resin preform within an open blow mould without mutual engagement of said handle and preform; said handle including upper retaining means and lower retaining means and said preform including a moulded engagement portion adapted to engage with the upper retaining means of the handle;
(b) causing the upper retaining means of the handle to interconnect with the engagement portion of the preform after the handle and preform have been separately positioned within the blow mould; and
(c) stretch blow moulding the preform in the blow mould wherein said blow moulding stretches the preform beneath the engagement portion into the blow mould to form a container and expands the side wall of the preform so to retain the upper retaining means of the handle in interconnecting relation with the engagement portion of the preform and so to secure and integrate the lower retaining means of the handle within the body of the formed container.
In another aspect of the invention there is provided a method of manufacturing a handled plastic container which includes the steps of:
a) positioning a preformed handle and a synthetic resin preform within an open blow-mould without mutual engagement of said handle and preform; said handle having an upper retaining means in an upper portion of said handle and a free end and said preform including a moulded engagement portion adapted to engage with said upper retaining means of the handle;
b) causing the upper retaining means to interconnect with the engagement portion of the preform after the handle and the preform have been separately positioned within the blow mould; and
c) stretch blow moulding the preform in the blow mould wherein the said blow moulding stretches the preform beneath the engagement portion into the blow mould to form a container and expands the side wall of the preform so to retain the upper retaining means of the handle in interconnecting relation with the engagement portion of the preform.
The upper retaining means of the handle may be interconnected with the engagement portion of the preform either prior to or after closing the blow mould. Preferably, the handle and preform are disposed within the open blow mould so that the upper retaining means of the handle is adjacent to but not interconnected with the engagement portion of the preform. The blow mould is thereafter closed and the preform pushed down so to effect engagement of the upper retaining means within the moulded engagement portion. Preferably the blow mould is shaped so to allow the preform to be moved downwardly from its original position within the blow mould by a distance of between about 1 to 4 mm so to enable interconnection of the preform with the handle. Conveniently, the preform is pushed down by the blow nozzle intended for use in introducing the high pressure gas into the preform to cause stretch blow moulding.
Preferably the handle and the preform can be positioned within the blow mould substantially simultaneously. In a most preferred embodiment the handle and preform are positioned in the mould by a single transfer arm which holds them both but where the handle and preform are not mutually engaged with each other. The handle may also be inserted into the blow mould marginally earlier or later than the preform and the side wall of the preform and the top of the handle may be respectively shaped so that the preform may slide across the top of the handle when being positioned adjacent to the handle in the blow mould.
Preferably both the handle and preform are transferred into the blow mould in planes which are substantially parallel.
The upper retaining means and the moulded engagement portion may be of various shapes and configurations. Whatever the configuration, the engagement portion on the preform should resist vertical (upwards) or horizontal detachment of the upper retaining means once interconnected;
Preferably, the upper retaining means of the handle is a lug or protrusion disposed at or adjacent the end of the top of the handle. In such arrangement, the moulded engagement portion of the preform is preferably in the form of a flange located beneath a neck finish on the preform, the flange including a depending lip so to provide a downwardly facing groove into which the lug or protrusion at the end of the handle may be retained. Alternatively, the flange may include an aperture into which the lug may be inserted.
Some preforms used on the commercial stretch blow moulding of containers include a flange beneath the container neck finish. This flange (often referred to as the xe2x80x9csupport ledgexe2x80x9d) has many purposes including the mechanised transfer of the preform to and from a blow mould and the support of the preform within the blow mould during the introduction of high pressure gas to blow mould the container.
Alternative arrangements of an appropriately shaped retaining means on the handle and a co-operating engagement portion on the preform will be self evident to persons skilled in the art. For example, it is possible to reverse the arrangements described above so that a downwardly facing lug is provided on the preform and an aperture or groove formed within an upper portion of the handle.
Preferably, the upper retaining means of the plastic handle extends from a curved support surface shaped to follow the geometry of the preform immediately beneath the moulded engagement portion. Such a support surface assists in the positioning and location of the upper retaining means for proper engagement with the moulded engagement portion of the preform. Where a support surface is provided its inner diameter should match the outside diameter of the preform. The arc length of the support ring may vary but it is found that it is easier to insert the handle into conventional blow moulding tools when the arc is relatively short.
In the embodiment of the invention where the handle includes a support surface which follows the geometry of the preform, it is particularly preferred that the handle also include a recessed portion adjacent to the support surface which comprises one or more ribs. In such arrangement, when the preform is blown, the portion of the preform immediately adjacent the support surface will expand into the recessed portion but less so in those areas comprising ribbing. As a consequence, once the bottle is blown the ribs in the recessed portion will be located within small indentations on the container and the ribs and indentations will thus co-operate to resist rotational movement of the handle.
The lower retaining means of the handle is preferably a lug or protrusion extending from the lower end of the handle. It should be shaped so that on blow moulding of the preform expansion of the side wall will capture and secure the lug within the formed body of the container. It may be of various geometrical shapes. Most preferably a lug which incorporates a hook or other extension is utilised so to encourage secure engagement with the body of the container.
The handle may be of any suitable configuration. In one embodiment of the invention, the container formed is blow moulded so to include a recess on one side suitable for accommodating the handle. Preferably, this recess includes a ledge onto which the bottom part of the handle may rest. In this configuration, it is preferred that the handle be generally xe2x80x9cCxe2x80x9d shaped in configuration with the upper and lower retaining means being at opposite ends. In a particularly preferred embodiment, the cross section of the handle is xe2x80x9cUxe2x80x9d shaped so to include terminal flanges and a connecting web. It is preferred that the terminal flanges face downwardly at the lower end of the handle so that a hollow is formed under the connecting web. In this embodiment, the lower retaining means may be a lug extending from the web. When configured in this way, the blow moulding of the preform in the vicinity of the lug forms a container side wall which fills the hollow formed by the flanges underneath the connecting web and thus securely retains the lug in position.
The handle may also include reinforcing ribs. In the embodiment described above in which the handle has terminal flanges extending from a web so to create a hollow on the underside of the handle it is preferred to strengthen the terminal flanges with ribbing as this area is exposed to high forces exerted by the expanding side wall of the preform during the blow moulding process. Preferably, the handle is formed by injection moulding. It is not necessary that it be made from the same plastics material as the bottle and it may be formed from a plastic such as high density polyethylene, polypropylene, PET, recycled PET, glass reinforced PET and glass reinforced high density polyethylene. The handle could also be made from a metal such as aluminium. The bottle and the handle can be made from the same material and this is preferably PET or recycled PET. This would enhance recycling of the bottle.
In accordance with a further aspect of the present invention there is provided a preform suitable for use in the method hereinbefore described. In particular, such a preform includes a base, an elongate side wall portion and a neck; the said neck including a preformed finish and beneath said finish an outwardly extending flange; said flange including a moulded engagement portion adapted to engage with either an aperture or lug on a handle. Preferably, the engagement portion is in the form of a lip depending from the outer edge of the flange. The preform may be made from any stretch blow mouldable polymer. Preferably, it is formed from a PET homopolymer or copolymer (whether virgin or regrind), or a multilayer structure which may include layers consisting of one or more of PET, PEN, EVOH or other polymers used in multilayer technology.
In accordance with a further embodiment of the invention, there is provided a handled plastic container, said container comprising a blow moulded plastic bottle and a separate handle interconnected thereto wherein said handle comprises upper retaining means and lower retaining means and said bottle includes a moulded engagement portion which is interconnected with the upper retaining means of the handle and wherein the lower retaining means of the handle is secured and integrated into the side wall of the container.
In yet another aspect of the invention there is provided a handled plastic container, said container comprising a blow moulded plastic bottle and a separate handle having a free end and interconnected to said bottle at another end by upper retaining means, said upper retaining means including a lug or protrusion, and the bottle including a neck finish having an engagement portion co-operable with said lug or protrusion connecting said upper retaining means with said bottle.